1. Field of the Invention
The present invention is directed to a breath actuated pulmonary drug delivery device used in the delivery of fluid dispensations from a drug-containing canister. The delivery device provides a metered dose of drug or other therapeutic agent when the patient inhales from the device.
2. Brief Description of Related Art
There are a variety of inhalation devices which release aerosol medication, either in a continuous spray or in a predetermined amount of medication, commonly referred to as a metered dose. The spray is applied directly into the patient's mouth, nasal area or respiratory airways. Typically, these devices are actuated by the pressure applied by the user's fingers, button action, or other related manual techniques. While there are devices which are activated by the inhalation of the users, some of which are very satisfactory, as with all things, variations or improvements are desirable.
Metered dose aerosol canisters of the medicine to be inhaled into the mouth, nasal areas or respiratory airways are manufactured by a variety of pharmaceutical companies. Metered dose aerosols are much the same as non-metered aerosol except that when the valve is depressed, a continuous spray is not discharged. Instead, a predetermined measured volume is discharged as a spray, releasing a fixed amount of medication. Examples of such metered dose inhalers are disclosed in U.S. Pat. No. 5,544,647, entitled "Metered Dose Inhaler"; and U.S. Pat. No. 5,622,163 entitled "Counter for Fluid Dispensers"; and U.S. patent application Ser. No. 09/241,010 filed Feb. 1, 1999 entitled "Metered Dose Inhaler Agitator" (commonly assigned), the disclosures of which are incorporated herein by reference.
A wide variety of fluid dispensers are known and commercially available to dispense metered proportions of a contained fluid from containers. For example, U.S. Pat. No. 3,749,290 describes a trigger actuated dispensing pump assembled with a fluid container. Upon actuation, a measured proportion of the contained fluid is dispensed from the containers.
"Pumping" type inhalers are known in the art. The device may be manually pumped (such as described in U.S. Pat. No. 5,284,132) or a pumping like cycle may be utilized. The medication may also be repeatedly released from a pressurized disposable canister to create repeated sprays or inhalations as needed.
Proper use of these manually actuated devices requires that the spray be activated at the beginning of the inspiratory cycle, so that the medication is carried into the lungs rather than being deposited in the mouth or throat. If this actuation is not correctly coordinated with the inspiratory phase, the metered dose may be deposited differently with each actuation and potentially compromise the therapeutics and safety of the product. A breath actuated device helps eliminate this problem by making the product easier to coordinate and more patient friendly, with predictable delivery and dispersion in the respiratory airways.
There are numerous factors leading to poor coordination of actuation of the spray and the inspiration cycle. Included in those factors are the inherent limitations of the users (if any), such as impaired physical abilities associated of geriatric patients or the as-yet-undeveloped skills of children, or their inability of either group to comprehend the correct way to use the device. Recognizing the need for correct and accurately delivered doses in the asthmatics, COPD patients and, as with other patients with other respiratory illnesses, a reliable breath activated device would improve the quality of life for these afflicted people.
Metered dose inhalers are, at present, the most efficient and best-accepted means for accurately delivering medications in measured doses to an animal's respiratory tract. Therapeutic agents commonly delivered by the inhalation route include bronchodilators (B2 agonists and anticholinergics), corticosteroids, and anti-allergics. Inhalation may also be a viable route for anti-infective, vaccinating, systemically acting and diagnostic agents, as well as anti-leukotrienes, anti-proteases and the like.
Metered dose inhalers are available in several types. Most frequently, metered dose inhalers comprise a chamber into which a pressure resistant container (canister) is placed. The container is typically filled under super-atmospheric pressures with a product such as a drug dissolved in a liquefied propellant, or micronized particles suspended in a liquefied propellant. The container is fitted with a metering valve. The valve is movable from an inner (charging) position to an outer (discharging) position. A spring bias holds the valve in the charged position until forced to the discharge position. Actuation of the metering valve allows a metered portion of the canister content to be released, whereby the pressure of the liquefied propellant carries the dissolved or micronized drug particles out of the container and to the patient. A valve actuator also functions to direct the aerosol as a spray into the patient's oropharynx. Surfactants are usually dissolved in the aerosol formulation and can serve the dual functions of lubricating the valve and reducing aggregation of micronized particles.
Representative of pharmaceutical formulations for use in metered dose inhalers are those described in U.S. Pat. No. 5,190,029. The metered dose inhalers for administering such pharmaceutical formulations are also well known as seen for example in the descriptions given in U.S. Pat. Nos. 3,361,306; 3,565,070; and 4,955,371 which are incorporated herein by reference thereto.